One document matched: draft-previdi-spring-problem-statement-00.txt
Network Working Group S. Previdi, Ed.
Internet-Draft C. Filsfils, Ed.
Intended status: Standards Track Cisco Systems, Inc.
Expires: August 17, 2014 B. Decraene
S. Litkowski
Orange
M. Horneffer
R. Geib
Deutsche Telekom
February 13, 2014
SPRING Problem Statement and Requirements
draft-previdi-spring-problem-statement-00
Abstract
The ability for a node to specify a forwarding path, other than the
normal shortest path, that a particular packet will traverse,
benefits a number of network functions. Source-based routing
mechanisms have previously been specified for network protocols, but
have not seen widespread adoption. In this context, the term
'source' means 'the point at which the explicit route is imposed'.
This document outlines various use cases, with their requirements,
that need to be taken into account by the Source Packet Routing in
Networking (SPRING) architecture.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on August 17, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Dataplanes . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. IGP-based MPLS Tunneling . . . . . . . . . . . . . . . . . . . 4
4. Fast Reroute . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Traffic Engineering . . . . . . . . . . . . . . . . . . . . . . 5
6. Interoperability with non-SPRING nodes . . . . . . . . . . . . 6
7. OAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8. Security . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
10. Manageability Considerations . . . . . . . . . . . . . . . . . 7
11. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
13.1. Normative References . . . . . . . . . . . . . . . . . . . 8
13.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
The ability for a node to specify a forwarding path, other than the
normal shortest path, that a particular packet will traverse,
benefits a number of network functions, for example:
Some types of network virtualization, including multi-topology
networks and the partitioning of network resources for VPNs
Network, link, path and node protection such as fast re-route
Network programmability
OAM techniques
Simplification and reduction of network signaling components
Load balancing and traffic engineering
The term 'source' means 'the point at which the explicit route is
imposed'.
In this context, Source Packet Routing in Networking (SPRING)
architecture is being defined so as to address the use cases and
requirements described in this document.
2. Dataplanes
The SPRING architecture should be general in order to ease its
applicability to different dataplanes.
MPLS dataplane doesn't require any modification in order to apply a
source-based routed model (e.g.:
[I-D.filsfils-spring-segment-routing-mpls]).
IPv6 specification [RFC2460] defines the Routing Extension Header
which provides IPv6 source-based routing capabilities.
The SPRING architecture should leverage existing MPLS dataplane
without any modification and leverage IPv6 dataplane with minor
modifications.
3. IGP-based MPLS Tunneling
The source-based routing model, applied to the MPLS dataplane, offers
the ability to tunnel services (VPN, VPLS, VPWS) from an ingress PE
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to an egress PE, without any other protocol than IGPs (ISIS or OSPF).
LDP and RSVP-TE signaling protocols are not required.
The SPRING architecture should allow PE to PE forwarding according to
the IGP shortest path without the addition of any other signaling
protocol. The packet each PE forwards across the network will
contain (within their label stack) the necessary information derived
from the topology database in order to deliver the packet to the
remote PE.
4. Fast Reroute
FRR technologies have been deployed by network operators in order to
cope with link or node failures through pre-computation of backup
paths.
The SPRING architecture should address following requirements:
o support of FRR on any topology
o pre-computation and setup of backup path without any additional
signaling (other than the regular IGP/BGP protocols)
o support of shared risk constraints
o support of node and link protection
o support of microloop avoidance
Further illustrations of the problem statement for FRR are to be
found in [I-D.francois-sr-resiliency-use-case].
5. Traffic Engineering
Traffic Engineering has been widely addressed using IGP protocol
extensions (for resources information propagation) and RSVP-TE for
signaling explicit paths. Different contexts and modes have been
defined (single vs. multiple domains, with or without bandwidth
admission control, centralized vs. distributed path computation,
etc).
In all cases, one of the major components of the TE architecture is
the signaling protocol (RSVP-TE) which is used in order to signal and
establish the explicit path. Each path, once computed, need to be
signaled and state for each path must be present in each node
traversed by the path. This incurs a scalability problem especially
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in the context of SDN where traffic differentiation may be done at a
finer granularity (e.g.: application specific). Also the amount of
state needed to be carried in all involved nodes contributes
significantly to complexity and the number of failures cases, and
thus increases operational effort while decreasing overall network
reliability.
The source-based routing model allows traffic engineering to be
implemented without the need of a signaling component.
The SPRING architecture should support traffic engineering,
including:
o loose or strict options
o bandwidth admission control
o distributed vs. centralized model (PCE, SDN Controller)
o disjointness in dual-plane networks
o egress peering traffic engineering
o load-balancing among non-parallel links
o Limiting (scalable, preferably zero) per-service state and
signaling on midpoint and tail-end routers.
o ECMP-awareness
o node resiliency property (i.e.: the traffic-engineering policy is
not anchored to a specific core node whose failure could impact
the service.
6. Interoperability with non-SPRING nodes
SPRING must inter-operate with non-SPRING nodes.
An illustration of interoperability between SPRING and other MPLS
Signalling Protocols (LDP) is described here in
[I-D.filsfils-spring-segment-routing-ldp-interop].
Interoperability with IPv6 non-SPRING nodes will be described in a
future document.
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7. OAM
The SPRING WG should provide OAM and the management needed to manage
SPRING enabled networks. The SPRING procedures may also be used as a
tool for OAM in SPRING enabled networks.
OAM problem statement and requirements will be described in a
separate document..
Interoperability with IPv6 non-SPRING nodes will be described in a
future document.
8. Security
There is an assumed trust model such that any node imposing an
explicit route on a packet is assumed to be allowed to do so. In
such context trust boundaries should strip explicit routes from a
packet.
For each data plane technology that SPRING specifies, a security
analysis must be provided showing how protection is provided against
an attacker disrupting the network by for example, maliciously
injecting SPRING packets.
9. IANA Considerations
TBD
10. Manageability Considerations
TBD
11. Security Considerations
TBD
12. Acknowledgements
TBD
13. References
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13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
13.2. Informative References
[I-D.filsfils-spring-segment-routing-ldp-interop]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R.,
Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe,
"Segment Routing interoperability with LDP",
draft-filsfils-spring-segment-routing-ldp-interop-00 (work
in progress), October 2013.
[I-D.filsfils-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R.,
Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe,
"Segment Routing with MPLS data plane",
draft-filsfils-spring-segment-routing-mpls-00 (work in
progress), October 2013.
[I-D.francois-sr-resiliency-use-case]
Francois, P., Filsfils, C., Decraene, B., and R. Shakir,
"Use-cases for Resiliency in Segment Routing",
draft-francois-sr-resiliency-use-case-00 (work in
progress), January 2014.
Authors' Addresses
Stefano Previdi (editor)
Cisco Systems, Inc.
Via Del Serafico, 200
Rome 00142
Italy
Email: sprevidi@cisco.com
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Clarence Filsfils (editor)
Cisco Systems, Inc.
Brussels,
BE
Email: cfilsfil@cisco.com
Bruno Decraene
Orange
FR
Email: bruno.decraene@orange.com
Stephane Litkowski
Orange
FR
Email: stephane.litkowski@orange.com
Martin Horneffer
Deutsche Telekom
Hammer Str. 216-226
Muenster 48153
DE
Email: Martin.Horneffer@telekom.de
Ruediger Geib
Deutsche Telekom
Heinrich Hertz Str. 3-7
Darmstadt 64295
DE
Email: Ruediger.Geib@telekom.de
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